Problem: Solve for $r$ : $18 = r - 17$
Add $17$ to both sides: $ \begin{eqnarray} \\ \hphantom{18 {+ 17}} &\hphantom{=}& \hphantom{r} \\ 18 &=& r - 17 \\ \\ {+17} && {+17} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ 18 {+ 17} &=& r \\ \end{eqnarray} $ Simplify. $ r = 35$